1. Field of the Invention
The present invention concerns an amplifier device having an amplifier circuit and an energy supply device. A radio-frequency, low-energy signal pulse can be amplified into a power pulse by the amplifier circuit. The amplifier circuit is supplied with electrical energy by the energy supply device.
2. Description of the Prior Art
Amplifier devices of the above type are generally known. They are in particular used for generation of transmission pulses for RF transmission coils in magnetic resonance systems. Other applications, for example in radar systems, are also possible.
In magnetic resonance systems the requirements for the power pulses to be output vary to a significant extent. This applies both for the duration of an individual pulse and for its maximum power and its average power as well as for the required currents and voltages.
It is of course possible to design the amplifier circuit and the energy supply device such that they operate properly in all operating states even though the energy supply device is permanently connected to the amplifier circuit, and the output voltage emitted by the energy supply device is kept constant, or optimally constant. In practice, however, this approach leads to significant power losses in the amplifier circuit in many operating situations. The power losses are significantly higher than when the amplifier circuit is operated with voltage values that are adapted to the respective operating state of the amplifier circuit.
The adaptation of the voltage value leads to a reduction of the power loss that occurs in the amplifier circuit, but in many cases it leads to significant power losses in the energy supply device. The problem is thus only shifted, but is not solved.
An amplifier device of the aforementioned type, in which the energy source is fashioned as a primary energy source that can be connected to the amplifier circuit via a primary coil and a secondary coil of a transformer, is known from U.S. Pat. No. 3,319,175. The secondary coil has multiple taps so that the voltage that is applied to the amplifier circuit can be adjusted as needed.